Airborne polystyrene nanoplastic exposure leads to splenic cell senescence and immune imbalance

Recently, the widespread detection of microplastics and nanoplastics in the human body and their potential health risks have aroused global concern. As nanoplastics are much smaller than microplastics in diamter, their features, such as larger specific surface areas, and greater biopenetration, may lead them to have greater potential toxic effects on human. Research specifically focused on the biological effects of nanoplastics is still in its early stages. The spleen is an essential immune organ, but there is still a lack of research on the effects of airborne nanoplastics on its immune function. It's still not clear about the situation human occupational or environmental inhalation exposure to polystyrene nanoparticles which remains an evidence gap. Therefore, in this study, we investigated the impact of nanoparticles on the structure and function of the spleen by simulating airborne exposure under laboratory conditions. We use 100 nm polystyrene nanoplastics and expose mice for one or two weeks through inhalation. Based on histological observations, flow cytometry analysis and gene expression, we found atrophy of the spleen and immune imbalance after exposure. Mechanistic analysis revealed that airborne nanoplastics down-regulate Cdk1, directly blocking the cell cycle. Additionally, they interfere with the p53 pathway's expression, indirectly blocking the cell cycle by inhibiting DNA repair, which ultimately leads to splenocyte senescence. In conclusion, these findings not only provide strong evidence that airborne nanoplastics has a detrimental effect on the spleen, but also assist in health risk assessment, thereby promoting more scientific and environmentally friendly use of plastics.